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SN1, SN2, E1, E2


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Strong base
What kind of nucleophile do we use for SN2?
Weak base is okay
What kind of nucleophile do we use for SN1?
What kind of product do we get for SN2?
Inversion due to backside attack (if we have chiral center)
What kind of product do we get for SN1?
Racemization; mixture of both dash/wedge (if we have chiral center)
Requires protic to stabilize the carbocation
What kind of solvents must we use for SN1?
Aprotic solvents (sometimes polar protic is okay)
What kind of solvents do we use for SN2?
3>2
What type of electrophile reacts the best in SN1?
1>2>3
What type of electrophile reacts the best in SN2?
rate = k [Nu][E]
What is the rate law for SN2 reactions?
rate = k [E]
What is the rate law for SN1 reactions?
F < Cl < Br <I
What is the ideal Leaving group for SN1/SN2 reactions?
Durinig E2 reactions:
What are the two exceptions to Anti-Zaitsev rule?
What is an E2 elimination?
Forms an alkene in an anticoplanar mechanism
HI + alkene
Markovnikov addn of Br and H. BR on most subbed
H2SO4/H2O aka H3O+
Markovnikov addn of H and OH. OH on most subbed.
H+/ROH
Markovnikov addn of H and OR-. OR on most subbed
HBr/H2O
What are the 3 possible carbocation rearrangements?
Cl2/CCl4
Backside attack causing Markovnikon anti addn of Br and Br
Cl2/H2O
Markovnikov anti addn of Br and OH. OH on most subbed
Br2/ROH
Markovnikov anti addn of Br and RO-. RO on most subbed
HBr/ROOR
Antimarkovnikov addn of Br and H
What is a Grignard Reagent used for?
To create carbon-carbon bonds to extend carbon chain length! A Grignard is a very strong carbon nucleophile made from organometallic reagents. Grignards CANNOT react with anything protic (i.e. has an H bonded to F…
What is an acetylide ion and what is it used for?
An acetylide ion is a strong nucleophile that is made by deprotonating an alkyne used to create carbon-carbon bonds to extend carbon chain length!
To which side do we attack an epoxide in acid? Not in acid?
In acid, epoxides get a (+) charge, which make them carbocation like. We must attack the most substituted side because of stability.
Reagents
Hydroboration- oxidation of an alkyne...
Ketones!
Addition of H2O to an alkyne can create...
Alkene + Br2/hv yields...?
You get 2 products:
We use:
How do we brominate at the allylic position of an alkene?
Initiation:
Free Radical Halogenation
What are the requirements of being aromatic?
Must pass rules 1-3 and have even number of pairs of pi electrons
What are the requirements of being nonaromatic?
Does not satisfy at least one or more of rules 1-3
When do you count lone pairs of electrons and when do you not in determining aromaticity?
Count lone pairs of electrons- When they are not near a double bond, the lone electrons are responsible for resonance of the structure, which contributes to the pi system
Benzylic Oxidation
is used for...
Electrophilic Aromatic Substitution
Substituting a benzene's hydrogen for an electrophile.
What is Friedal-Craft Alkylation?
Benzene + RX or ROH with AlCl3/FeBr3/AgNo3 catalyst
What is Friedal-Craft Acylation?
Benzene + carbonyl electrophile
Electron DONATING groups
Electron rich species that:
Electron WITHDRAWING groups
Electron poor species that:
Activating (electron donating groups) + the halogens
What are the Ortho/para directors (1,3) for EAS?
What are the meta directors for EAS?
Deactivating (electron withdrawing groups) - the halogens
The donating ALWAYS wins! So we direct in ortho/para position.
If a benzene has both a donating and withdrawing group on it, which one directs an incoming substituent?
If you have 2 donating groups on a benzene ring, which one directs an incoming substituent?
The one that is the more donating one wins. How do we know? The one that is the LEAST ELECTRONEGATIVE is the MOST donating to the benzene (nucleophile), causing it to become LESS STABLE, and thus, MORE REACTIVE.
Grignard/organolithium or acetylide ion
How do we extend carbon chain lengths? i.e. create carbon-carbon bonds
acid chloride> anhydride> ester > amide > carboxylate
List the carboxylic derivatives from most reactive to least reactive...
acid chloride would bc it has the best LVG.
Which of the following would react the fastest with OH- ?
carboxylate ion
Carboxylic Acid derivatives react with H2O/OH- to produce...
carboxylic acid
A compound that contains the carboxyl grp, --COOH
Williamson Ether synthesis
Alkoxide + primary/secondary halide
XS HBr...
Ethers only react with....
Stronger than PCC.
What is Chromic Acid used for?
What is PCC used for?
Oxidizes primary alcohol to aldehyde
What do alcohols usually react with and why?
OH is a poor leaving group, so most of the time, alcohols react with halides to create good LVG.
Alcohol dehydration
H2SO4. Loses water to form an alkene